Folding square.



P. KRIGHBAUM.

FOLDING SQUARE. APPLICATION FILED MAY 18, 1909.

Patented Aug. 30, 1910.

INVENTOR v BY ATTORNEY R5 cu WASHINGTON, n. 6.

WITNESSES IVE/4,44%?

PAUL KRICHBAUM, OF SAN FRANCISCO, CALIFORNIA.

FOLDING SQUARE.

Specification of Letters Patent.

Patented Aug. 30, 1910.

Application filed May 18, 1909. Serial No. 496,700.

T 0 all whom it may concern:

Be it known that I, PAUL KRIoHBAUM, a citizen of Austria-Hungary, residing at San Francisco, in the county of San Francisco and State of California, have invented new and useful Improvements in Folding Squares, of which the following is a specification.

The object of the present invention is to provide a folding square which will be simple in construction and durable in use, Will be very accurate in form when extended for use, and which can be so extended and moved into the position for use with a small amount of friction.

In the accompanying drawing, Figure 1 is a broken side view of the square extended for use; Fig. 2 is a similar view of the same closed; Fig. 3 is a cross section on the line 33 of Fig. 2.

Referring to the drawing, 1 indicates the main member or blade of the square, and 2 the smaller member or tongue. The member 1 is formed with a projection 3 extending laterally therefrom, and of a thickness substantially one-half of that of the main portion of said member, and the member 2 is also formed with a projection 4 extending laterally therefrom and of substantially onehalf its thickness. Adjacent to said exten sion 3, the middle portion of the main member 1 is also cut away in thickness or recessed, as shown at 5, the contour of such recessed portion corresponding to that of the extension 4: from the secondary member 2; and, in like manner, the secondary member 2 is cut away or formed with a recess or shallow portion 6, having a contour corresponding to that of the extension 3 from the main member. Said extension 3 of the main member and the secondary member are pivoted together by means of a rivet 7.

By reason of the above construction, when the secondary member 2 turns on said pivot with reference to the main member 1, its extension 4 is adapted to enter the recess or shallow portion 5 of the main member, and at the same time the extension 3 of the main member is adapted to enter the recessed or shallow portion 6 of the secondary member. On account of the internal-contour of the recess of each member corresponding with the external contour of the extension from the other member, said extensions exactly fit said recesses, when the square is fully opened out, so that there is no gap, or

lack of continuity, between the edges of said parts. When in this position the hook 9 of a latching lever 10 pivoted at 11 in a recess 12 in the edge of the main member engages a notch 13 formed in the edge of the secondary member at its end and prevents said latter member moving away from a position at right angles to the main member. A spring 141 in said recess engages the tail 15 of said lever and maintains it in its operative position. Said latch is provided at the side with a nick or recess 16 like that in a knife blade, so that it can be withdrawn from its locking position when desired. The outer end of the latch is formed with a beveled impact edge 17, and the advancing portion of the secondary member, in front of the notch, is formed with a correspondingly sloping front edge 18, adapted to engage the beveled edge 17 to the latch, so that when the square is opened out, it is readily secured in its operative position.

Each part of the periphery of each projection is so curved that the center of curvature thereof is at the side of the pivot toward which the projection moves from the open to the closed position of the square. Thus, as shown by dotted lines in Fig. 1, the center of curvature of the first part of the projection or tongue 3 is a point a, which lies to the left of the lines drawn from the center of the pivot 7 to this portion of the periphery, and of the succeeding part is a point I), which again is to the left of the lines drawn from the center of the pivot 7 to said portion of the periphery in the same way, the center of curvature of the small end of the projection 4 is a point a, which is to the left of lines extending from the center of the pivot 7 to said portion of the periphery,

and the center of curvature of the succeeding portion of said projection 4 is at b, which is also to the left of lines extending from the center of the pivot to said portion of the periphery.

The edge of each recess is formed along its whole length with an undercut bevel, as shown at 21, and the edge of each extension is formed along its whole length with a bevel 22 arranged to fit snugly in the undercut beveled edge of the corresponding recess of the other member, thereby insuring a snug fit when the square is opened out and preventing any movement of one member out of the plane of the other.

The direction of the projections from the two members, the blade and the tongue,

form an important feature of my invention.

Each projection extends in a direction transverse to the general direction of the member from which it projects, and, since it fits snugly in a correspondingly shaped recess in the other member, it results that said members, when in their open position at right angles to one another, are firmly held in said position against relative movement in any direction.

By reason of the above construction there is very little wear upon the edges of the parts which fit into each other, or of the rivet. Moreover, the accuracy of the square by no means depends upon any nice adjustment or fit of the rivet, but depends entirely upon the fit of the extension in the corresponding recesses and in the co-engagement oi' the latch and notch.

I claim A folding square comprising two members, a blade and a tongue, pivoted together, to assume positions either parallel with, or at right angles to, each other, the terminal portion of the long edge of the tongue, adj acent to its pivoted end, being, in said latter position, in contact with the short edge of the blade at said end, each of said members having in one side a shallow recess, and a projection extending from said member transversely to its general direction, and of the same form as the recess in the other member, the edge of each recess being formed throughout its whole length with an undercut bevel, and the edge of each projection being formed with a bevel along its whole length arranged to fit snugly in the undercut beveled edge of the corresponding recess of the other member, the periphery of each projection having curvatures of finite radii with centers at that side of the pivot toward which the projection moves from the open to the closed position of the square, and means for securing said members in the position in which said projections fit in said recesses, substantially as described.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

PAUL KRIOHBAUM. \Vitnesses F. M. TRIGI-IT, D. B. RICHARDS. 

